SEA ANCHOR FAQ'S Bridling (including Multihulls & Monohulls) Use of chain Rode (Size/Length) Trip Lines Surplus Parachutes as Sea Anchors Sea Anchors "Spinning" Strengths vs Loads and Holding Power Sizing Considerations The Drag Device Data Base Supplemental Instructions for commercial fishermen or overnight layovers
Bridling MULTIHULLS All Multihulls MUST use a bridle to both hulls (abase). Each leg should be a minimum of two and a half times the beam of the boat. The overall scope of rode, including the bridle length, should be about 11 to 12 times the LOA or longer. The bridle legs MUST be attached to both hulls. WARNING - Some catamarans have a centrally located anchor roller situated midbeam on the weakest part of the boat - the aluminum crossbar that supports the trampoline. On these boats leading one of the bridle legs there MUST NOT BE DONE. It is not braced like a mast and attaching to it can lead to failure of the crossbar, capsize and loss of life. We learned this because someone did just such an attachment (against the instruction manual) which lead to failure of the crossbar, capsize and LOSS OF LIFE!!! See page 10 of the Sea Anchor Instructions. ATTACHING BRIDLE LEGS NOTE - Make sure cleats or pad eyes have substantial backing plates. If you are cleating off the bridle legs you MUST use substantial chafe protection, be prepared to check for chafe often and let some rode out if experiencing chafe. You can shackle the bridles to the hulls using thimbled rode ends and shackles. This eliminates the need for chafe gear provided the bridle legs are not rubbing on any part of the boat. You can use snatch blocks on one or both bows as fairleads routing the bridle legs (make sure they are long enough to reach) back to solid connection points (cleats, etc.). One bridle leg could be fixed, or both adjustable which will allow you to change the angle on the bow for a more comfortable ride. Be aware of chafe between the snatch blocks and the connection points and check for it often. BRIDLE JUNCTION There are three ways of assembling the bridle/main rode junction: Thimbles in the ends of each bridle leg and the end of the main rode - make sure you use one shackle on each bridle leg. DO NOT attach all three thimbled ends to one shackle as
the thimbled ends will bind against each other. This setup allows flexibility in that you have three ropes to work with if you need them for other uses. Thimble in the end of the main rode and a "Y" bridle which is attached to the main rode with one shackle. This type of bridle is best made with single braid rope as it can be threaded through itself and can not separate. DIRECT SPLICED BRIDLE This is a main rode/bridle as one unit. The main rode goes from the Sea Anchor to the boat and one bridle leg is spliced into the rode at the bridle leg length from the boat. Imagine a huge dock loop which has been cut in two. Again, this type of bridle setup is best made with single braid rope. MONOHULLS Lin and Larry Pardey, in their book "STORM TACTICS" advocate the use of a bridle to hold the boat in a hove-to attitude for greater stability and ride comfort. We believe that securing the boat at some angle to the weather can make a difference in how the boat rides and the degree of comfort. Use Of Chain WITH SEA ANCHORS We recommend use of some chain between the Sea Anchor and the boat. CHAIN AT THE SEA ANCHOR If you are planning on cleating the main rode to your boat (with SUBSTANTIAL chafe protection) then we recommend using a short length of chain at the Sea Anchor to aid deployment and create some catenary effect. Chain at the Sea Anchor helps keep the Sea Anchor down. During slack cycles the chain causes the Sea Anchor to swing down and maintain some tension in the rode.
MID-SCOPE CHAIN Although our instruction manual illustrates chain mid-scope, input from the field (to the Drag Device Data Base by Victor Shane) suggests it does not have the effect we had believed. One report we received tells of a 40' sloop in a hurricane with 200' of rode, 40' of chain with a 45# CQR mid-chain and then another 200' of rode. The report is that the rode and chain were straight and the anchor was thrashing about the chain. Placing chain midscope is the busiest place, requiring thimbles in the rode ends and shackles to join the chain to the rode. For these reasons we tend to lean away from mid-scope chain. CHAIN AT THE BOAT This is where chain can provide the most benefit. It prevents the rode from chafing through (which is our biggest concern). You can let out a few feet in moderate conditions to well over 100' in severe conditions. There are a few things you need to be aware of: Remove the anchor from the end of the chain - if you are unable to remove the anchor you MUST use a short length of chain as a "stand off" to keep the anchor flukes away from the rode because an anchor which is thrashing about could chafe through the rode with its flukes. The chain MUST be snubbed to the deck cleats to off load the windlass. We carry Stainless Steel Chain Grabbers for this purpose (they fit 5/16" to 1/2" chain). Once you are set on the Sea Anchor it is virtually impossible to adjust the amount of chain which is out so you must determine the sea conditions and let out the appropriate amount when the Sea Anchor is initially set. (See the section "Bridling with Chain"). The down side to using chain at the boat is that the chain can do damage to the chocks, bow roller, etc. but we believe the trade off of not having to be concerned with the rode's chafing through is worth the possible damage. CHAIN/RODE CONNECTIONS We are not in favor of spliced chain/rode connections. We prefer thimbles in the ends of the rode and shackling the ends to the chain. This is a little problematic as the "weak link" is often the size of the shackle screw pin. A shackle with a screw pin which will fit through the chain link may often be weaker than the chain and the rode. The proper size
shackle may have a screw pin which is too large to fit through the chain link. It is important that the strength of all components be as close as possible to matching. One way to get past this is to use the proper sized bow shackle attached to the rode and attaching that shackle to the chain via a Titanium "D" Shackle. This is a little busier but the bow shackle can be attached to the rode and moused leaving just the titanium shackle to be attached to the chain. CHAIN & DROGUES It is well established that the use of a length (10 to 15 feet) of chain between a Drogue and the rode will help keep the Drogue down and improve its performance. Rode We have always advocated NYLON rode for use with Sea Anchors due to its ability to stretch and absorb energy. Recommended sizes are in the Sea Anchor Instructions and are based on feedback to the Drag Device Data Base by Victor Shane. You can use a larger size than recommended but you should not go smaller. ALWAYS buy the best rope you can possibly afford. REMEMBER, your life may depend on it!!! MAIN TYPES OF ROPE 3-Strand Twisted - This is by far the most common type of rope construction and the least expensive as virtually everyone makes it. The down side is that some manufacturers use the cheapest yarn to keep the price competitive. The worst part of 3-strand is that it has a tendency to twist or unlay when under load. This twisting and untwisting has been known to generate heat which weakens the rope. Also, this twisting and untwisting makes the rope an unruly mess when you try to stow it after it has been loaded as it wants to twist, knot and hackle. NOTE: A good swivel can absorb some of these torsional loads during slack cycles. Double Braid - This is also a very common construction and generally a little stronger than 3-strand twisted. It does not twist when under load but has less stretch due to its construction. Having inner and outer components the two parts can generate friction between them which can weaken the rode. It is generally more expensive than 3-strand
twisted. If the core (inner section) herniates, or bulges outside the outer part, the rope must be discarded or the damaged part cut out and the ends re-spliced. Single Braid- The least common construction - but we believe it is the best construction for use with Sea Anchors - it does not twist under load or generate heat during load and unload cycles and has good stretch characteristics. It is usually the most expensive rope you can buy. Nylon Yarn- Over the years we have learned that there is a significant difference in the various types of nylon yarn used to make rope. Ropes made from Type 6-6 yarn are FAR superior to ropes made from Type 6 yarn both in their elasticity and their resistance to ultraviolet degradation. ASK your rope supplier what yarn their rope is made from - DO NOT tell them what you are seeking - MAKE THEM TELL YOU WHAT IT IS MADE FROM. Otherwise they will just say it's made from the yarn you want. RODE LENGTH For severe storms we recommend 10 to 15 times the LOA. For overnight layovers in moderate conditions very short rodes have been used, however it is EXTREMELY important that if you use a short tether you pay particular attention to the "Hazards of Wave Particle Rotation" section in the Sea Anchor instruction book. 3 Lengths - Short, Intermediate, Storm Short - A short rode is one which is within 1/3 of a wave phase - if the distance between crests is 100' then a short rode would be about 33' or less. There is little chance of enough energy build up to break the rode or damage the Sea Anchor. The rode should be no longer than this 1/3 wave phase. This length is commonly used for drift fishing in light to moderate conditions and fairly flat seas. This distance is more critical in seas where there is a definite running swell as you can easily get into the intermediate length requirement. Intermediate - Rode length of 35' to 300'. Within this range of rode length it is critical that the boat and Sea Anchor be "IN PHASE" - BOTH are on the crest and in the trough at the same time. If not in phase the boat and Sea Anchor will converge (move towards one another), creating slack in the rode and then diverge (move away from one another). When they diverge they are accelerating away from one another and when the slack is taken out of the rode something has to give. If the rode is long enough (storm length) it should have sufficient stretch to absorb the energy of this acceleration. If the rode is not long enough any one of the following can occur - the Sea Anchor blows a panel (preferred occurrence as the Sea Anchor will still work), the rode will break or a cleat will fail (you lose your hold on the sea). This length is generally used on overnight layovers and when fishing. It
is the most critical rode length to use. Again, pay particular attention to the "Hazards of Wave Particle Rotation" section of the instruction manual. Storm - In severe storms there are three main reasons for the 10 to 15 times LOA length: There is so much tension on the rode that to be constantly adjusting the length to be in phase with the waves is a practical impossibility. In a severe storm the seas will be confused with irregular swells and the long rode length will tend to mitigate the effects of being out of phase. The long length of NYLON rode provides for some give or shock absorption in the system which leads to less stress on the Sea Anchor, rode and attachment hardware. RODE/STOW DEPLOYMENT BAGS These bags are designed to make rode deployment as easy as possible. The rode is attached to the Sea Anchor and the boat and the bag is tossed overboard with the Sea Anchor where the rode deploys automatically. The rode passes through the bag and the bag is held captive to the system. One of the considerations in using Rode Stow/D'bags is the amount of rode in each bag. Many cruisers are couples and putting 400' of 3/4" rode in one bag would make the bag weigh over 60 Lbs. Imagine the stronger person being injured and the weaker person having to deploy the Sea Anchor. With this in mind we generally will split the rode into two lengths which must be shackled together. This is a little busier but is more manageable for a person with limited strength. Trip Lines There are many opinions with respect to the use of trip lines to recover Sea Anchors. Some prefer to use a full trip line which comes all the way back to the boat. These users are usually fishermen who use their Sea Anchors as a tool for overnight layovers and persons who actively use their Sea Anchor. Some prefer to not use any trip line at all. Usually with smaller Sea Anchors. Still others prefer a "partial" trip line which floats free and must be motored up to to recover the Sea Anchor.
A trip line is a line attached to a Sea Anchor as an extension of the Float Line (which is an integral part of the Sea Anchor and goes from the apex [top center] of the Sea Anchor to the surface). A float (usually a large fender, referred to as the Primary Float) is attached to the Float Line and this float controls the maximum depth the Sea Anchor is allowed to go. Note that when under load the Sea Anchor will ride virtually at the surface. During recovery, when the Sea Anchor is unloaded, it hangs like a jellyfish by the float and Float Line. Without the float on the end of the Float Line the Sea Anchor could hang upside down in an open position. This is VERY DANGEROUS as the Sea Anchor can literally pull the bow under if allowed to open in this attitude. PARTIAL TRIP LINES We recommend the use of at least 20' (preferably 50 to 100') of 1/4" to 3/8" polypropylene line for a partial trip line. You should attach something that floats to the end of the trip line. This allows you to fetch up on the trip line and still be away from the Sea Anchor. The 20' minimum is so when you get to the trip line you are lifting a limp line onto the deck from the waterline. This has to do with LEVERAGE. Without a trip line you will be lifting the float and float line, with everything hanging below it, from the waterline to the deck. A trip line allows you to get the line on deck before any lifting is done. Partial Trip Lines are easier to deploy but recovery requires motoring up to the Trip Line in order to recover the Sea Anchor, which can be challenging in somewhat turbulent conditions. FULL TRIP LINES A full trip line goes from the Primary Float all the way back to the boat. Use of a Full Trip Line makes recovery very easy. You take all the slack out of the Trip line, cleat it off, then let out the main rode which will automatically "trip" the Sea Anchor. It's then a simple matter of pulling in the Sea Anchor by the Trip Line. It does take a little more care in deploying a Sea Anchor with a Full Trip Line. Some of the early pioneers of Sea Anchor use, John & Joan Casanova, used a full trip line for Eighteen Years while cruising on two different multihulls and deploying their parachute [Sea Anchor] in storms of every description with no difficulty. If not using a trip line, the common practice is to literally pull the boat to the Sea Anchor. With 6' and 9' Sea Anchors it is usually not that difficult but with larger Sea Anchors (and thus larger boats) it becomes increasingly more difficult and you risk equipment (rode, cleat, etc.) failure when the Sea Anchor and boat get out of phase with respect to wave particle rotation (see hazards of Wave Particle Rotation in the Sea Anchor instructions).
BEING TAKEN UNDER TOW If you are laying on a Sea Anchor because your boat is disabled and you are about to be towed, a Trip Line will make being taken under tow far safer. You can direct the tow boat to the Trip Line. They will be upwind of you and several hundred feet away, virtually eliminating any chance of collision. They would pull the Trip Line on board, followed by the Sea Anchor and the rode, cleat the rode and take you under tow. If you are using a Full Trip Line attach a float to the end and toss it over for them to fetch up on. TRIP LINES Our Partial Trip Lines are 100' polypropylene lines in their own stow/deployment bags with integral float. The bags are red for visibility and can be used as a heaving line if needed. They are also available in longer lengths but 100' is adequate. Our Full Trip Lines are 1/4" Nylon (to stretch as the rode stretches during wave cycles). They come in their own stow bag. Length is determined by Sea Anchor size and rode length. Surplus Parachutes As Sea Anchors When we started in the Sea Anchor business the only "Sea Anchors" we sold were government surplus 24' and 28' personnel parachutes which we set up for use as Sea Anchors. These parachutes performed adequately but over time we found their durability to be poor. Our first customers were the local sport fishermen who used them mainly for overnight layovers and wore them out regularly, sometimes as often as twice a season. Durability, cost and availability lead us to make our own parachutes specifically for use as Sea Anchors. Occasionally we are asked about surplus parachutes for use as a Sea Anchor. There are many different parachutes out there and we are familiar with very few. This is not to say that none of them are usable as a Sea Anchor. If we are not familiar with a particular one we are asked about we won't offer an opinion as to its suitability. If it is sent to us we can evaluate it and offer our opinion. Many parachutes can be altered for use as a Sea Anchor but the main question is durability. We have no objection to setting up a surplus parachute as a Sea Anchor but we WILL NOT be responsible for the structural integrity of any particular parachute. The parachute may hold enough water to hold your boat but not be durable enough to endure the duration of a storm.
WARNING From time to time "rock crawlers" (people who crawl out from under their rock, rip people off and then crawl away) offer surplus parachutes representing them as "sea anchors"... some of these rock crawlers claim "one size fits all". DON'T YOU BELIEVE IT!!! One of these rock crawlers had the nerve to claim that the sea anchors he was selling were government surplus sea anchors. THEY WERE NOT!!! We got one and they were made of mosquito netting with no structural integrity at all. They actually were flare parachutes left over from the Vietnam War. That rock crawler is located in Annapolis, MD. If you have one contact us IMMEDIATELY - DO NOT USE IT. BUYER BEWARE - If you are not sure what you have purchased please give us a call, your safety and well being is our NUMBER ONE concern "Spinning" Sea Anchors 1. "Spinning" Sea Anchors - We have heard stories of the Float Line and Trip Line becoming twisted together and tangling, supposedly because the Sea Anchor was "spinning" in the water. While surplus parachutes are built in a way that can lead to rotation, Sea Anchors are manufactured in a way that any rotation is "built out" and underwater video of a Sea Anchor being towed has shown there is no rotation. 2. Float Line & Trip Line Twisted Together - There have been reports of the Float Line and Trip Line becoming twisted together. While this has been credited to the Sea Anchor "spinning" our observation is that the Primary Float is the culprit. All three items (Float Line, Trip Line & Primary Float) join at the same point and there is no tension on the Trip Line. Surface action on the Primary Float causes it to spin around and, with no tension on the Trip Line, the Trip Line gets wound around the Float Line. Our solution is to attach a small swivel to the end of the Float Line. The Trip Line is attached to the same side of the swivel as the Float Line. The Primary Float is attached to the free side of the swivel, separating its motion from the Float Line/Trip Line. 3. Deployment Bag caught in Lines - On Sea Anchors built prior to 1998, the Bag could rise to the surface. On the surface the Bag would fill with water. In breaking seas the water filled Bag could be subject to wave crest capture and be thrown over the Sea Anchor and into the lines. On all Sea Anchors built after 1998, there is a ring attached to the Float Line about two feet from the apex of the Sea Anchor. This ring holds the Bag well below the surface and out of the wave crest.
Strengths Vs Loads and Holding Power We often hear comments referring to the strain on the rode when tethered to a Sea Anchor in severe weather. These comments all have the same thing in common - the strain on the rode is HUGE. But just how high is the strain?? We believe the strains appear to be higher than they really are. WHY?? APPEARANCES CAN BE DECEIVING Put a 1,000 pound load on a 10,000 pound tensile strength rope and the rope will appear to be very close to breaking when in reality it is loaded to only 10% of its strength. Commercial fishermen have used surplus 24' and 28' parachutes for years. We know from our own tug testing that the 24' parachutes will fail at a load of 4,000 pounds. Call it 5,000 pounds for a 28'. Those fishing boats are in the 50 to 60 foot range displacing from 45,000 to 85,000 pounds. Data Base File S/P-2 is from a 65', 85,000# F/V on a 28' parachute in 18' seas and 45-55 Kt. winds. The loads COULD NOT HAVE BEEN 5,000 pounds or the parachute WOULD HAVE FAILED (see #3 below). Another boat - 50' LOA and 70,000# regularly used 1/2" rode (7,000# Tensile Strength) with a 28' (5,000#) parachute. From wind load charts in various publications a 60' power boat in 42 Kt. Winds generates 4,000# of pull and 8,000# of pull in 60 Kt. Winds Assuming these numbers are accurate and adding anything at all for wave forces then the 28' parachute in S/P-2 should have failed in 55 Kt. Winds but it didn't Equivalent Sea Anchors are two to four times the overall strength of surplus parachutes. Our system recommendations are based on the premise that the Sea Anchor is the "weak link" and when extreme stresses are experienced (like a wave breaking over the wheel house of a fishing boat) the Sea Anchor will blow a panel to relieve the stress but still hold the boat when a surplus parachute would fail totally. RECOMMENDATIONS Our recommendations are based on years of input to the Drag Device Data Base by Victor Shane. We have made changes to our products and recommended components because of this input. Our general rule of thumb is when in doubt go to the larger size - Sea Anchor,
rode, hardware, etc. We look at the LOA of the boat first then the weight or displacement then the type of boat (S/V, P/V, Multihull, etc.). For offshore use in potential heavy weather with breaking seas the minimum size we recommend, regardless of boat size, is 12'. Any smaller Sea Anchor would likely be caught in the crest of a breaking wave and be completely tumbled and collapsed (See Sea Anchor Sizing Considerations). The following chart illustrates the "holding power" of Sea Anchors. There is NO WAY any Sea Anchor could take these kind of loads and the displacement numbers are best viewed strictly with respect to the amount of water a parachute Sea Anchor displaces - they have no bearing as to the strength of the Sea Anchor. In the Sept., 1999 issue of Yachting World we were daises by a contributor who experienced a less than satisfactory ride on an 18' Sea Anchor while in a storm aboard his 55', 50,000# ketch. Seems the author and W.W.II's editors overlooked a small point. AT NO TIME has recommended an 18' Sea Anchor for a boat over 50' LOA. In the chart note that the 18' Sea Anchor has has less than 50% of the holding power of a 24'. Sea Anchor Size Water Displacement Recommended Boat LOA Boat Displacement 6 Foot 2,400 Lbs. Under 20 Feet to 4,000 Lbs. 9 Foot 9,900 Lbs. Under 25 Feet to 8,000 Lbs. 12 Foot 23,500 Lbs. 25 to 33 Feet to 12,000 Lbs. 15 Foot 45,500 Lbs. 30 to 40 Feet to 25,000 Lbs. 18 Foot 79,400 Lbs. 35 to 48 Feet to 40,000 Lbs. 24 Foot 188,000 Lbs. 40 to 90 Feet to 95,000 Lbs. 32 Foot 446,000 Lbs. 70 to 120 Feet to 200,000 Lbs. 40 Foot 871,000 Lbs. 120 to 150 Feet to 300,000 Lbs.
Sea Anchor Sizing Considerations OFFSHORE STORM CONDITIONS The MINIMUM size Sea Anchor we recommend for this application is our 12 foot for the following reason: WAVE CREST CAPTURE In confused or breaking seas the breaking part of the wave can extend 8' deep or more. A Sea Anchor smaller than 12 feet caught in this breaking crest will be fully captured and tumbled causing the Sea Anchor to completely lose its grip on the sea. With the Sea Anchor no longer holding, the boat will fall off and be in danger of being rolled. By using a LARGE DIAMETER parachute Sea Anchor of at least 12 feet in diameter, if the seas are breaking 8' deep the lower 4' of the Sea Anchor will remain in the non breaking part of the sea and will maintain its grip on the sea. Once the breaking wave passes the Sea Anchor is then able to reset itself and fully hold the boat. This is the reason we advocate the use of LARGE DIAMETER parachute Sea Anchors. NOTE: ALL Sea Anchors, when under load in storm conditions, will ride right at the surface. Anyone who says otherwise is not being accurate. OFFSHORE IN MODERATE CONDITIONS Overnight layovers when fishing, etc. - you can follow the sizing guidelines on the Sea Anchor page. The Drag Device Data Base Following a successful solo crossing from Santa Barbara to Honolulu and back in 1979 aboard his 24 Foot trimaran"providence" and aided by a surplus parachute as a Sea Anchor, Victor Shane set out to catalog and disseminate accurate information about the use of Sea Anchors and Drogues. Thus was born the Drag Device Data Base (DAB). An added impetus was the 1979 FASTEN tragedy where several boats and lives were lost - lives and boats that could well have been saved had they been aware of modern drag devices.
Now in its fourth edition, completely revised and updated, we consider the DAB to be the best work available on the subject of offshore drag devices - Sea Anchors and Drogues. Because of the real world contributions from drag device users to the DAB we have made refinements in our Sea Anchors to make them more "user friendly" and have also refined our sizing and rigging recommendations. The DAB is an ongoing work and we are constantly in touch with the author to swap information. Every drag device goes out with a DAB Response Form - we want to know what works the best and where improvements can be made. The DDDB is a worthwhile addition to your library of cruising books and is available from us for $36.95. Supplemental Instructions For using your Sea Anchor for overnight layovers- fishing trips, etc. RODE LENGTH For storm use we recommend a length of at least 10 times the LOA of the boat. This length is to mitigate the effects of being out of phase with respect to the HAZARDS OF WAVE PARTICLE ROTATION (see pg. 13 of the instruction manual). In confused seas the phase will not remain constant, which would make it necessary to constantly adjust the rode length. But the strain on the rode in such conditions so high that it is virtually impossible to make such adjustments so adjusting the scope is generally done because of chafe. This is not the case in moderate conditions where the strain on the rode is much lower. In any case it is easiest to let our additional rode to get "in phase". On overnight layovers in moderate conditions a much shorter rode can be used. However, you MUST pay particular attention to the HAZARDS OF WAVE PARTICLE ROTATION and make sure the Sea Anchor and Boat are "in phase". If conditions deteriorate and a longer rode is necessary you need to be prepared to let out as much as 10 times the LOA of your boat, or more. This may entail shackling a second or third rode to the primary rode.
TRIP LINES The use of a FULL Trip Line (all the way back to the boat) for overnight layovers will make recovery much easier. Extra care should be taken during deployment to keep from getting the Trip Line wrapped around the Sea Anchor. The Full Trip Line should be 1/4" Nylon and at least the length of the rode plus the size of the Sea Anchor. Once the Sea Anchor is set, excess slack should be taken out of the Trip Line but it should not be tight. RECOVERY WITH A FULL TRIP LINE The easiest way to recover your Sea Anchor with a Full Trip Line is to take all the slack out of the trip line and cleat it off. Next let out the anchor rode. As the rode is let out the Sea Anchor will "trip" (turn upside down) and collapse on itself. It is then a simple matter to pull the Sea Anchor in via the Trip Line. Courtesy of Paratech Engineering - Manufacturer of these Sea Anchors, Sea Breaks and Drouges.